Power control system for vehicle disk motor

ABSTRACT

A brushless D.C. disk motor has one or more disk rotor assemblies and pairs of stator assemblies for each rotor assembly. Each disk rotor assembly has a disk and a plurality of permanent magnets distributed along two or more circular paths in the disk inboard of the peripheral edge of the rotor. Each stator assembly has a plurality of pole pieces and coils distributed along a mounting plate in corresponding circular paths. The disk is rotatably mounted to a support member; while the stator sub-assemblies are fixed to the support member. The coils are selectively activated by commutated power control signals generated in response to a vehicle condition parameter, such as vehicle speed or disk motor load, to optimize power drain from the source of electrical power in accordance with the value of the vehicle condition parameter.

BACKGROUND OF THE INVENTION

This invention relates to brushless D.C.motors used for the propulsionof vehicles. More particularly, this invention relates to a powercontrol system for a brushless D.C. vehicle propulsion motor with a moreefficient design for optimizing power application to the motor.

Brushless D.C. vehicle propulsion motors are known and have been usedfor the propulsion of many different types of vehicles, such asbicycles, motorcycles, autos, and small trucks. A typical motor designhas a rotor and a stator. The rotor is fixedly attached to the vehiclewheel for rotation therewith; the stator is attached to a vehiclestationary member, such as the fork of a bicycle or motorcycle frame. Aspecific type of brushless D.C. motor is a disk motor. In a disk motor,both the rotor and the stator typically comprise disks having circulargeometry, with the rotor disk being rotationally arranged between twoflanking stator disks. The rotor disk usually carries a plurality ofpermanent magnets mounted along a circular path centered on therotational axis of the rotor disk. In some disk motors the permanentmagnets are mounted along only one circular path; in others, thepermanent magnets are mounted along two or more concentric circularpaths. The stator disks are fixedly mounted to the vehicle and eachstator disk carries a plurality of electromagnets distributed in one ormore matching circular paths centered on the axis of the stator diskwith essentially the same radii as the circular paths of the permanentmagnets on the rotor disk. The coils of the electromagnets are typicallycoupled to a multi-phase driving circuit, usually in a three-phasearrangement. Electrical power for the driving circuit is supplied by aD.C. power source, such as a lead-acid battery, and a power conversioncircuit is used to convert the D.C. electrical power from the battery tomulti-phase pulse or A.C. power signals for synchronously driving theelectromagnets mounted on the stator disks to provide rotating magneticfields which interact with the rotor permanent magnets to provide thedriving forces for the rotor. Typically, the electromagnets are groupedin phases, with all electromagnets in the same phase group being drivenin unison and electromagnets in different phase groups being driven withdifferently phased power signals. A manually operable control circuitallows the frequency or the duty cycle of the power signals produced bythe driving circuit to be varied, which causes the rotor to be driven atdifferent rotational speeds by the rotating magnetic fields produced bythe electromagnets. Rotor position signals generated by individualposition sensors (such as Hall effect sensors) mounted adjacent therotor at different angular positions, or by back EMF sensor circuitscoupled to the coils, provide position information to govern theswitching of the power signals to the next commutation state. A motorspeed feedback signal is supplied to the control electronics. For ageneral discussion of brushless D.C. motor propulsion techniques,reference may be has to Application Note AVR:443 entitled “Sensor-basedcontrol of three phase Brushless DC motor” published by AtmelCorporation of San Jose, Calif. Examples of known multi-phase A.C.vehicle propulsion motors are shown in U.S. Pat. Nos. 6,100,615;6,276,475 and 6,617,746, and U.S. Patent Application Publication NumberUS 2002/0135220 A1, the disclosures of which are hereby incorporated byreference.

The basic disk motor configuration described thus far can be expanded toinclude several rotors and stators laterally spaced along the rotationalaxis of the disk motor. In such configurations, the driving circuitremains essentially the same, with multi-phase power signals beingapplied in parallel to the electromagnets mounted on the several statorplates.

In all known disk motor power control systems, the multi-phase pulsepower signals are applied to all of the electromagnets in the statordisks, regardless of the actual vehicle speed or load demand on the diskmotor. As a consequence, the energy demand on the battery power sourceis usually greater than that actually required by the disk motor inorder to provide the propulsion force ideally required under a given setof vehicle speed or load conditions. This excessive use of battery powerunduly limits the range of the associated vehicle and thus theperformance of known brushless D.C. motor vehicle propulsion systems.

SUMMARY OF THE INVENTION

The invention comprises a power control technique for brushless D.C.vehicle disk motors which is devoid of the limitations noted above inknown disk motor power control designs, and which is therefore capableof affording greater vehicle range on a given battery charge andproviding greater vehicle range for a battery of given energy storagecapacity.

In the broadest apparatus aspect, the invention comprises an electricvehicle propulsion system comprising:

a disk motor having at least one rotor disk having a peripheral edge anda plurality of permanent magnets distributed along a plurality ofessentially circular substantially concentric paths, the paths beinglocated inwardly of the peripheral edge; and a stator assemblypositioned in facing relation to the rotor disk, the stator assemblyhaving a mounting plate with a peripheral edge, a plurality of polepieces distributed on the mounting plate along a plurality ofessentially circular substantially concentric paths located inwardly ofthe peripheral edge of the mounting plate, and a plurality of coils eacharranged about a corresponding one of the plurality of pole pieces, theplurality of coils being grouped into a plurality of phase groups,preferably three phase groups; and

a power control circuit for supplying commutated power control signalsto the coils in a manner determined by at least one current vehiclecondition, the power control circuit including a source of electricalpower; a vehicle condition parameter source for manifesting anelectrical signal representative of a vehicle condition parameter; acontroller having an input for receiving the electrical signal and aplurality of outputs for manifesting inverter control signals generatedin response to the value of the electrical signal; and a plurality ofinverters each having an input coupled to a different one of thecontroller outputs and a plurality of outputs for generating commutatedpower control signals for individual ones of the plurality of coils ofthe stator assemblies, each inverter having an associated set of statorcoils and each one of the inverter outputs being coupled to a differentone of the plurality of phase groups of the associated set of statorcoils so that individual sets of stator coils can be selectivelyactivated to optimize power drain from the source of electrical power inaccordance with the value of the electrical signal. Preferably, when thecoils are grouped into three phase groups the commutated power controlsignals applied to three phase groups of stator coils have a phaseseparation of substantially 120 degrees. Preferably, the vehiclecondition parameter source can be a vehicle speed sensor for sensingcurrent vehicle speed, or a vehicle load sensor for sensing the existingload on said disk motor.

The power control circuit may further include a vehicle operatorcontrollable vehicle speed controller for generating an electricalsignal representative of desired vehicle speed; and the controller mayinclude a second data input for receiving the electrical signalsrepresentative of desired vehicle speed so that the individual sets ofstator coils can be selectively activated to optimize power drain fromthe source of electrical power in accordance with the value of theelectrical signal representative of a vehicle condition parameter andthe electrical signal representative of desired vehicle speed.

The controller preferably includes a collection of set point vehiclecondition parameter values for specifying the individual sets of statorcoils to be selectively activated. The set point vehicle conditionparameter values can be vehicle speed set point values or disk motorload set point values.

The disk motor may include a pair of stator assemblies positioned inflanking relation to the rotor disk, with each of the stator assemblieshaving a mounting plate with a peripheral edge, a plurality of polepieces distributed on the mounting plate along a plurality ofessentially circular substantially concentric paths located inwardly ofthe peripheral edge of the mounting plate, and a plurality of coils eacharranged about a corresponding one of the plurality of pole pieces, theplurality of coils being grouped into a plurality of phase groups. Thedisk motor may be further expanded into a plurality of axially spacedrotor assemblies and stator assembly pairs.

From a process standpoint, the invention comprises a method ofcontrolling the application of electrical commutated power signals to adisk motor having at least one rotor disk with a peripheral edge and aplurality of permanent magnets distributed along a plurality ofessentially circular substantially concentric paths, the paths beinglocated inwardly of the peripheral edge; and a stator assemblypositioned in flanking relation to the rotor disk, the stator assemblyhaving a mounting plate with a peripheral edge, a plurality of polepieces distributed on the mounting plate along a plurality ofessentially circular substantially concentric paths located inwardly ofthe peripheral edge of the mounting plate, and a plurality of coils eacharranged about a corresponding one of the plurality of pole pieces, theplurality of coils being grouped into a plurality of stator sets andphase groups, the method comprising the steps of:

-   -   (a) providing a source of electrical power;    -   (b) generating a vehicle condition parameter signal        representative of a vehicle condition parameter;    -   (c) determining the value of the vehicle condition parameter        signal;    -   (d) generating a plurality of power control signals from the        value of the vehicle condition parameter signal; and    -   (e) applying the plurality of power control signals to phase        groups of selective ones of the stator coil sets to optimize        power drain from the source of electrical power in accordance        with the value of the vehicle condition parameter signal.

The vehicle condition parameter signal may be representative of currentvehicle speed or the existing load on the disk motor.

The method may further include the steps of:

-   -   (f) generating an electrical signal representative of desired        vehicle speed;    -   (g) determining the value of the desired vehicle speed signal;        and    -   (h) using the value of the desired vehicle speed signal in        steps (d) of generating and (e) of applying so that the        individual sets of stator coils are selectively activated to        optimize power drain from the source of electrical power in        accordance with the value of the vehicle condition parameter        signal and the electrical desired vehicle speed signal.

The disk motor may include a pair of stator assemblies positioned inflanking relation to the rotor disk, each of the stator assemblieshaving a mounting plate with a peripheral edge, a plurality of polepieces distributed on the mounting plate along a plurality ofessentially circular substantially concentric paths located inwardly ofthe peripheral edge of the mounting plate, and a plurality of coils eacharranged about a corresponding one of the plurality of pole pieces, theplurality of coils being grouped into a plurality of stator sets andphase groups. When applied to this motor construction the step (e) ofapplying is performed on phase groups of selective ones of the statorcoil sets of both stator assemblies.

The invention has wide application to a variety of vehicles, such as anautomobile, a bicycle, a motorcycle, and the like. Electric vehiclepropulsion systems fabricated according to the teachings of theinvention are capable of being operated in a much more efficient mannerthan disk motors in which the stator coils are operated continuously inparallel. Specifically, only those stator set coils which are necessaryto provide the optimum propulsion force to the vehicle are activated,which extends the useful life of the electrical energy stored in abattery power source. Consequently, a smaller battery can be used in anelectrically powered vehicle propulsion system to obtain the same rangeof such a system using conventional stator coil activation techniques.In addition, given a battery of a specific energy capacity, a disk motoroperated in accordance with the teachings of the invention can achieve alonger range than a disk motor operated according to conventionaltechniques.

For a fuller understanding of the nature and advantages of theinvention, reference should be made to the ensuing detailed descriptiontaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view taken along the longitudinal axis of a diskmotor having a single rotor and a pair of flanking stators;

FIG. 2 is a front plan view of the rotor disk of the disk motor of FIG.1;

FIG. 3 is a front plan view of one of the two stators of the disk motorof FIG. 1;

FIG. 4 is a sectional view taken along lines 4-4 of the stator of FIG.3;

FIG. 5 is a schematic diagram of the disk motor power control system;

FIG. 6 is a block diagram of an inverter used in the power controlsystem of FIG. 5;

FIG. 7 is a flow chart illustrating operation of the disk motor powercontrol circuit;

FIGS. 8A-8C are power control signal waveform diagrams illustrating thepower control signals applied to the same phase group coils of threestator sets of coils;

FIG. 9 is a sectional view of a disk motor having three rotors and sixstators;

FIG. 10 is a schematic sectional view of the disk motor of FIG. 1adapted for use with an automobile wheel; and

FIG. 11 is a schematic sectional view of the disk motor of FIG. 1adapted for use with a spoked wheel.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning now to the drawings, FIG. 1 is a sectional view taken along thelongitudinal axis of a disk motor having a single rotor and a pair offlanking stators. As seen in this Fig., the disk motor includes a diskrotor assembly 20 and a pair of stator assemblies 30L, 30R. Disk rotorassembly 20 comprises a central disk member 21 rotatably mounted bymeans of a standard low friction bearing 22 to a mounting shaft 40.Shaft 40 is secured to the frame of a vehicle (not shown) and serves asthe mounting support for the disk motor. Shaft 40 may comprise an axlestub of an automobile, for example. Secured to opposing faces of diskmember 21 are a plurality of permanent magnets 25 i. Disk member 21 isfabricated from a non-magnetic material, such as Delrin, Nylon,aluminum, or any other relatively stiff non-magnetic material. Permanentmagnets 25 i are secured to disk member 21 using any one of a number ofknown techniques, such as adhesive bonding with a secure bondingadhesive (e.g. an epoxy resin adhesive); thermal bonding; welding; orthe equivalent. Disk member 21 is secured to an axially extendingcylindrical wall member 27, which is secured at each end to a pair ofend plates 28, 29 in contact with the outer race of bearings 22L, 22R,respectively.

Each stator assembly 30L, 30R comprises a mounting plate 32L, 32R, aplurality of pole pieces 34Li, 34Ri, and a plurality of coils 35Li, 35Rieach arranged about the outer circumference of an associated pole piece34Li, 34Ri. Pole pieces 34Li, 34Ri are fabricated from a suitablemagnetically susceptible material, preferably silicon steel, and aresecured to their respective mounting plates 32L, 32R using any suitablebonding technique such as a strong adhesive, welding, or the like.Mounting plates 32L, 32R are fixedly secured to shaft 40 so that thestator assembly 30 does not move on shaft 40.

As best seen in FIG. 2, permanent magnets 25 i are arranged about thetwo major opposing surfaces of disk member 21 in circular paths. In theembodiment of FIGS. 1 and 2 three concentric circular paths of permanentmagnets 25 i are disposed on each major surface of disk member 21. Thepermanent magnets 25 i in each circular path on one surface of diskmember 21 are physically arranged so that adjacent magnets in eachcircular path have magnetic orientation of opposite polarity. Inaddition, magnets 25 i mounted on opposite sides of disk member 21 inmutual registration have magnetic orientations of additive polarity.Still further, adjacent magnets 25 i in the different circular paths onthe same surface of disk member 21 are also arranged to have magneticorientations of opposite polarity. For example, adjacent magnets 25-12,25-1, and 25-2 in the outer circular path on disk member 21 have South(S)-North (N)-South (S) magnetic orientations (see FIG. 2). Magnet 25-1and its counterpart in the outer circular path on the opposite side ofdisk member 21 have additive N-S magnetic orientations. Magnet 25-1 inthe outer circular path of disk member 21 and magnet 25-13 in the middlecircular path on the same side of disk member 21 have N-S magneticorientations. Similarly, Magnet 25-13 in the middle circular path ofdisk member 21 and magnet 25-21 in the inner circular path of diskmember 21 have S-N magnetic orientations.

The magnetic orientations shown in FIG. 2 for magnets 25 i and labeledeither N or S denote the polarity of the magnetic field at the outersurface of each magnet 25 i. To illustrate, FIG. 2 shows magnet 25-1with an N orientation; and magnet 25-13 with an S orientation. Formagnet 25-1, the N signifies that the outer surface of magnet 25-1 isthe North pole of the magnet, while the South pole of magnet 25-1 is atthe inner surface which confronts the outer surface of disk member 21.Similarly, for magnet 25-13, the S signifies that the outer surface ofmagnet 25-13 is the South pole of the magnet, while the North pole ofmagnet 25-13 is at the inner surface which confronts the outer surfaceof disk member 21. Thus, these two magnets are arranged in amagnetically additive manner.

FIGS. 3 and 4 illustrate the physical arrangement of the pole pieces34Li and coils 35Li for the left stator assembly 30L. The right statorassembly has an identical physical layout. As seen in FIG. 3, polepieces 34Li are distributed on the surface of mounting plate 32L inthree concentric circular paths which match the circular paths describedby magnets 25 i on the rotor disk member 21. As seen in FIG. 4, eachcoil 35Li is arranged about a corresponding pole piece 34Li and securedthereto in any suitable fashion. The number of pole pieces 34Li and thenumber of coils 35Li is different from the number of magnets 25 i on thefacing side of rotor disk 21. The same is true for the number of polepieces 34Ri and the number of coils 35Ri of the right stator assembly30R.

Also with reference to FIGS. 3 and 4, for purposes of electricalconnection the coils 35Li are grouped into three sets: Stator set I,Stator set II, and Stator set III; and three phase groups: group A,group B, and group C. For the set grouping, in the outer circular pathcoils 35L1-35L9 constitute Stator set I; in the middle circular pathcoils 35L10-35L15 constitute Stator set II; and in the inner circularpath coils 35L16-18 constitute Stator set III. For the phase grouping,in the outer circular path coils 35L1, 35L4, and 35L7 are group A coils;coils 35L2, 35L5, and 35L8 are group B coils; and coils 35L3, 35L6, and35L9 are group C coils. In the middle circular path, coils 35L10, and35L13 are group A coils; coils 35L11 and 35L14 are group B coils; andcoils 35L12 and 35L15 are group C coils. In the inner circular paththere is only one coil per group-viz, coil 35L16 (group A); coil 35L17(group B); and coil 35L18 (group C). The coils 35Ri of the right statorsub-assembly 30R are similarly grouped.

FIG. 5 is a schematic diagram of the disk motor power control system. Asseen in this Fig., a controller 50 supervises the operation of aplurality of power inverters 51I, 51II, and 51III. The three phaseoutputs from each of the inverters 51I, 51II, and 51III are coupledrespectively to the three phase groups A-C of coils 35 i in theassociated stator sets I-III to provide commutated power signalsthereto. Controller 50 preferably comprises a microcontroller, such as atype AVR microcontroller available from Atmel Corporation of San Jose,Calif. Controller 50 receives real time data from three data sources: avehicle speed controller 53, a vehicle condition parameter sensor 54,and the rotor position sensors 55 in the disk motor. Vehicle speedcontroller 53 may comprise the accelerator pedal position sensor in anautomotive vehicle, the manually operable speed control of a motorcycleor a bicycle, or any other known operator controllable device forenabling the vehicle operator to alter the vehicle speed. Vehicleparameter condition sensor 54 may comprise a vehicle speed indicator, avehicle load sensor for sensing the existing load on the disk motor, orany other known device for supplying an electrical signal representativeof a vehicle parameter which affects the mode of operation of the diskmotor. Rotor position sensors 55 may comprise Hall effect sensorsmounted in preselected angular positions adjacent the disk rotor 20,back EMF sensor circuits, or any other known device for generating rotorangular position signals representative of rotor position referenced toa preselected angular reference point. Electrical power is supplied toelements 50, 51, 53, 54, and 55 by a suitable D.C. power source 57, suchas a battery or a combination of a battery and a regulator circuit.

FIG. 6 is a block diagram illustrating the major components of each ofthe inverters 51I, 51II, and 51III. As seen in this Fig., each inverterincludes a pulse generator 61 for generating commutated pulse signals inaccordance with synchronous control signals from controller 50. Pulsegenerator 61 emits three separate pulse trains with a phase separationof 120 degrees. The three pulse train output signals from pulsegenerator 61 are coupled to a preamplifier 62, and the three pulse trainoutputs of preamplifier 62 are coupled to a power amplifier in which thepulse signals are amplified prior to being coupled to the coils 35 i ofthe associated Stator set.

FIG. 7 is a flow chart illustrating operation of the power controlcircuit. Upon startup, controller 50 samples the data inputs from speedcontroller 53 and vehicle condition parameter sensor 54. Next,controller 50 selects the stator sets to be activated. This may be doneusing a table look-up routine which consults a stored table of vehiclecondition parameter values, speed controller values and stator setactuation rules. Next, controller 50 generates control signals to theinverters 51 i, which produce the power control signals for theappropriate stator sets. The process is repeated, changing the statorset actuation conditions in response to changes in the data inputs fromspeed controller 53 and vehicle condition parameter sensor 54.

The manner in which the various stator sets is controlled can bedetermined empirically or theoretically. The main criterion is toprovide the optimum set of power control signals to the stator setswhile minimizing power drain from the battery in the D.C. power source57. As an example, for an automotive application the following table ofvehicle speed versus activated stator sets is theoretically optimal forprolonging battery life:

Measured Vehicle Speed Activated Stator Sets 0.0 to 5.0 mph. I, II, andIII 5.1 to 15.0 mph. I and II 15.1 to 30.0 mph. I and III 30.1 to 45.0mph. II and III 45.1 to 60.0 mph. II only 60.1 and above mph. III onlyNote that this table only includes the actual measured vehicle speed asthe vehicle condition parameter signal. If the demanded vehicle speedsignals from speed controller 53 are also included, the relation betweenmeasured vehicle speed and activated stator sets can be altered to takeinto consideration the operators desire to accelerate the vehicle at afaster rate (although at the expense of greater energy drain from thebattery) or permit the vehicle to decelerate with none of the statorcoil sets activated (minimum power consumption).

In operation in the acceleration mode, with the vehicle at restcommutated power signals are initially applied to all three of thestator sets of coils until the vehicle attains a speed of 5.1 mph. Atthis set point, the application of commutated power signals is switchedso that power is applied to the coils in only stator sets I and II. Whenthe vehicle attains a speed of 15.1 mph, the application of commutatedpower signals is switched so that power is applied to the coils in onlystator sets I and III. When the vehicle attains a speed of 30.1 mph, theapplication of commutated power signals is switched so that power isapplied to the coils in only stator sets II and III. When the vehicleattains a speed of 45.1 mph, the application of commutated power signalsis switched so that power is applied to the coils in stator set II only.When the vehicle attains a speed of 60.1 mph, the application ofcommutated power signals is switched so that power is applied to thecoils in stator set III only.

In the deceleration mode, if the vehicle speed drops below 60.1 mph andthe operator wishes to maintain a speed of 60.1 mph or above, theapplication of commutated power signals is switched so that power isapplied to the coils in stator set II only. If the vehicle speed dropsbelow 45.1 mph and the operator wishes to maintain a speed between 45.1and 60.0 mph, the application of commutated power signals is switched sothat power is applied to the coils in stator sets II and III only. Ifthe vehicle speed drops below 30.1 mph and the operator wishes tomaintain a speed between 30.1 and 45.0 mph, the application ofcommutated power signals is switched so that power is applied to thecoils in stator sets I and III only. If the vehicle speed drops below15.1 mph and the operator wishes to maintain a speed between 15.1 and30.0 mph, the application of commutated power signals is switched sothat power is applied to the coils in stator sets I and II only. If thevehicle speed drops below 15.1 mph and the operator wishes to maintain aspeed between 0.0 and 15.0 mph, the application of commutated powersignals is switched so that power is applied to the coils in stator setsI, II and III.

In the deceleration mode the demanded vehicle speed signals may be usedto override the above table so that all stator coil sets are deactivatedwhen the vehicle operator wants the vehicle to coast to a lower speed.Similarly, when the vehicle is cruising at a given speed and the vehicleoperator wishes to accelerate at a great rate (e.g., when passinganother vehicle), the demanded vehicle speed signals may be used tooverride the above table and activate all stator sets to supply maximumpower to the disk motor.

As noted above, the vehicle condition parameter sensor may comprise avehicle load sensor for sensing the existing load on the disk motor. Forsuch an implementation, the switching set points for the stator coilsets will be based on disk motor load values instead of mphmeasurements. Thus, the application of commutated power signals to thestator coil sets will be switched in accordance with the measured loadvalues attaining certain threshold values. The actual set point valuesfor a given vehicle can best be determined on an empirical basis.

FIGS. 8A-8C illustrate the power signals applied to the stator sets forthe first three sets of power conditions set forth in the above table.In each of these Figs., the power signals are illustrated for only onephase of the three possible phases for each stator set. In FIG. 8A powersignals are applied to the phase A coils of all three of the statorsets. In FIG. 8B power signals are applied to the phase A coils ofstator sets I and II-no power signals are applied to the phase A coilsof stator set III. In FIG. 8C power signals are applied to the phase Acoils of stator sets I and III-no power signals are applied to the phaseA coils of stator set II. The power signals applied to the phase B andphase C coils of the three stator sets are controlled in a similarmanner but are phase displaced by 120 degrees from those illustrated inFIGS. 8A-8C.

While the invention has been thus far described with reference to a diskmotor having a single rotor assembly 20 and two flanking statorassemblies 30L, 30R, the invention is equally applicable to disk motorshaving different configurations. FIG. 9 illustrates one such alternateconfiguration. As seen in this Fig., a disk motor has three disk rotorassemblies; and three corresponding stator assemblies. Each of the diskrotor and stator assemblies is identical to that described above withreference to FIGS. 1-4. In this embodiment, end plates 71, 72 arerotatably mounted on support shaft 40 using low friction bearings 22L,22R; rotor disks 21L, 21C, and 21R are rotatably mounted on shaft 40using low friction bearings 22ML, 22C, and 22MR; and all of the statormounting plates 32 i are firmly secured to shaft 40 to prevent rotationof the stator assemblies 30 i.

FIG. 10 is a sectional view of the FIG. 1 disk motor adapted for use asa driving motor for the wheel of an automobile having a pneumatic tire80. As seen in this Fig., disk motor 10 is positioned concentrically oftire 80 and provides the propulsion force for the wheel. Wall enclosure27 can form an integral part of the rim of a wheel. Alternatively, wallenclosure 27 may be attached to the wheel in concentric fashion.

FIG. 11 is a sectional view similar to FIG. 10, but illustrating theapplication of the invention to a spoked wheel 91, such as one used onbicycles and motorcycles. As seen in this Fig., wheel 91 has a pluralityof individual spokes 92 connected between a rim 93 and the disk motorhousing. Disk motor assembly 10 is concentrically mounted with respectto the wheel 91, and may form the wheel hub. Shaft 40 can be connectedto the fork of the cycle.

Instead of providing separate permanent magnets positioned on oppositesurfaces of the rotor disk, the rotor disk may be provided with magnetapertures and a single magnet having a thickness greater than thethickness of the rotor disk may be installed in a given aperture witheach pole surface of the magnet extending out of the plane of the facingsurface of the rotor disk. This arrangement substantially reduces thetotal number of individual magnets needed and simplifies the magnetalignment procedure.

As will now be apparent, disk motors driven by the power control signalsaccording to the invention are operated in a much more efficient mannerthan disk motors in which the stator coils are operated continuously inparallel. Specifically, only those stator set coils which are necessaryto provide the optimum propulsion force to the vehicle are activated,which extends the useful life of the electrical energy stored in thebattery power source. Consequently, a smaller battery can be used in anelectrically powered vehicle propulsion system to obtain the same rangeof such a system using conventional stator coil activation techniques.In addition, given a battery of a specific energy capacity, a disk motoroperated in accordance with the teachings of the invention can achieve alonger range than a disk motor operated according to conventionaltechniques.

While the invention has been described with reference to particularembodiments, various modifications, alternate constructions andequivalents may be employed without departing from the spirit of theinvention. For example, while the embodiments illustrated and describeduse three concentric circular magnetic element paths, otherconfigurations may be employed using different numbers of circularpaths. In addition, the number of disk rotor assemblies and pairedstator assemblies incorporated into the motor housing may be expandedbeyond one, as desired. Also, although pulse control signals have beendisclosed as the form of commutated power signals applied to the statorcoils, A.C. signals can be employed, as desired. Therefore, the aboveshould not be construed as limiting the invention, which is defined bythe appended claims.

1. An electric vehicle propulsion system comprising: a disk motor havingat least one rotor disk having a peripheral edge and a plurality ofpermanent magnets distributed along a plurality of essentially circularsubstantially concentric paths, said paths being located inwardly ofsaid peripheral edge; and a stator assembly positioned in facingrelation to said rotor disk, said stator assembly having a mountingplate with a peripheral edge, a plurality of pole pieces distributed onsaid mounting plate along a plurality of essentially circularsubstantially concentric paths located inwardly of said peripheral edgeof said mounting plate, and a plurality of coils each arranged about acorresponding one of said plurality of pole pieces, said plurality ofcoils being grouped into a plurality of phase groups; and a powercontrol circuit for supplying commutated power control signals to saidcoils in a manner determined by at least one current vehicle condition,said power control circuit including a source of electrical power; avehicle condition parameter source for manifesting an electrical signalrepresentative of a vehicle condition parameter; a controller having aninput for receiving said electrical signal and a plurality of outputsfor manifesting inverter control signals generated in response to thevalue of said electrical signal; and a plurality of inverters eachhaving an input coupled to a different one of said controller outputsand a plurality of outputs for generating commutated power controlsignals for individual ones of said plurality of coils of said statorassemblies, each said inverter having an associated set of stator coilsand each one of said inverter outputs being coupled to a different oneof said plurality of phase groups of said associated set of stator coilsso that individual sets of stator coils can be selectively activated tooptimize power drain from said source of electrical power in accordancewith the value of said electrical signal.
 2. The invention of claim 1wherein said vehicle condition parameter source comprises a vehiclespeed sensor for sensing current vehicle speed.
 3. The invention ofclaim 1 wherein said vehicle condition parameter source comprises avehicle load sensor for sensing the existing load on said disk motor. 4.The invention of claim 1 wherein said power control circuit furtherincludes a vehicle operator controllable vehicle speed controller forgenerating an electrical signal representative of desired vehicle speed;and wherein said controller includes a second data input for receivingsaid electrical signals representative of desired vehicle speed so thatsaid individual sets of stator coils can be selectively activated tooptimize power drain from said source of electrical power in accordancewith the value of said electrical signal representative of a vehiclecondition parameter and said electrical signal representative of desiredvehicle speed.
 5. The invention of claim 1 wherein said controllerincludes a collection of set point vehicle condition parameter valuesfor specifying the individual sets of stator coils to be selectivelyactivated.
 6. The invention of claim 5 wherein said set point vehiclecondition parameter values are vehicle speed set point values.
 7. Theinvention of claim 5 wherein said set point vehicle condition parametervalues are disk motor load set point values.
 8. The invention of claim 1wherein said plurality of coils are grouped into three phase groups. 9.The invention of claim 8 wherein said commutated power control signalsapplied to said three phase groups of stator coils have a phaseseparation of substantially 120 degrees.
 10. The invention of claim 1wherein said disk motor includes a pair of stator assemblies positionedin flanking relation to said rotor disk, each of said stator assemblieshaving a mounting plate with a peripheral edge, a plurality of polepieces distributed on said mounting plate along a plurality ofessentially circular substantially concentric paths located inwardly ofsaid peripheral edge of said mounting plate, and a plurality of coilseach arranged about a corresponding one of said plurality of polepieces, said plurality of coils being grouped into a plurality of phasegroups.
 11. A method of controlling the application of electricalcommutated power signals to a disk motor having at least one rotor diskwith a peripheral edge and a plurality of permanent magnets distributedalong a plurality of essentially circular substantially concentricpaths, the paths being located inwardly of the peripheral edge; and astator assembly positioned in flanking relation to the rotor disk, thestator assembly having a mounting plate with a peripheral edge, aplurality of pole pieces distributed on the mounting plate along aplurality of essentially circular substantially concentric paths locatedinwardly of the peripheral edge of the mounting plate, and a pluralityof coils each arranged about a corresponding one of the plurality ofpole pieces, the plurality of coils being grouped into a plurality ofstator sets and phase groups, said method comprising the steps of: (i)providing a source of electrical power; (j) generating a vehiclecondition parameter signal representative of a vehicle conditionparameter; (k) determining the value of the vehicle condition parametersignal; (l) generating a plurality of power control signals from thevalue of the vehicle condition parameter signal; and (m) applying theplurality of power control signals to phase groups of selective ones ofthe stator coil sets to optimize power drain from the source ofelectrical power in accordance with the value of the vehicle conditionparameter signal.
 12. The method of claim 11 wherein the vehiclecondition parameter signal is representative of current vehicle speed.13. The method of claim 11 wherein the vehicle condition parametersignal is representative of the existing load on the disk motor.
 14. Themethod of claim 11 further including the steps of: (n) generating anelectrical signal representative of desired vehicle speed; (o)determining the value of the desired vehicle speed signal; and (p) usingthe value of the desired vehicle speed signal in said steps (d) ofgenerating and (e) of applying so that the individual sets of statorcoils are selectively activated to optimize power drain from the sourceof electrical power in accordance with the value of the vehiclecondition parameter signal and the electrical desired vehicle speedsignal.
 15. The method of claim 14 wherein the vehicle conditionparameter signal is representative of current vehicle speed.
 16. Themethod of claim 11 wherein the disk motor includes a pair of statorassemblies positioned in flanking relation to the rotor disk, each ofthe stator assemblies having a mounting plate with a peripheral edge, aplurality of pole pieces distributed on the mounting plate along aplurality of essentially circular substantially concentric paths locatedinwardly of the peripheral edge of the mounting plate, and a pluralityof coils each arranged about a corresponding one of the plurality ofpole pieces, the plurality of coils being grouped into a plurality ofstator sets and phase groups; and wherein said step (e) of applying isperformed on phase groups of selective ones of the stator coil sets ofboth stator assemblies.